GPII-4500: Fixed the "preference" metric.

[stegru]

Metric is captured when a preference has been applied.

From the snapset_2B preference set:

{
    module: "metrics",
    event: "preference",
    data: {
        name: "http://registry.gpii.net/common/cursorSize",
        setTo: "1"
    }
}
{
    module: "metrics",
    event: "preference",
    data: {
        name: "http://registry.gpii.net/common/DPIScale",
        setTo: "2"
    }
}
{
    module: "metrics",
    event: "preference",
    data: {
        name: "http://registry.gpii.net/common/highContrastTheme",
        setTo: "white-black"
    }
}

[gpii-bot]

CI job failed: https://ci.gpii.net/job/universal-tests/2353/

[gpii-bot]

CI job passed: https://ci.gpii.net/job/universal-tests/2355/

[javihernandez]

onCreate.trackPrefsSetChange?